A technique relates to protecting a tunnel junction. A first electrode paddle and a second electrode paddle are on a substrate. The first and second electrode paddles oppose one another. A sacrificial shorting strap is formed on the substrate. The sacrificial shorting strap connects the first electrode paddle and the second electrode paddle; The tunnel junction is formed connecting the first electrode paddle and the second electrode paddle, after forming the sacrificial shorting strap. The substrate is mounted on a portion of a quantum cavity. The portion of the quantum cavity is placed in a vacuum chamber. The sacrificial shorting strap is etched away in the vacuum chamber while the substrate is mounted to the portion of the quantum cavity, such that the sacrificial shorting strap no longer connects the first and second electrode paddles. The tunnel junction has been protected from electrostatic discharge by the sacrificial shorting strap.
Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. A method of forming a protected tunnel junction, the method comprising: forming a first electrode paddle and a second electrode paddle on a substrate, the first electrode paddle and the second electrode paddle opposing one another; forming a sacrificial shorting strap on the substrate, the sacrificial shorting strap connecting the first electrode paddle and the second electrode paddle; forming the tunnel junction connecting the first electrode paddle and the second electrode paddle, after forming the sacrificial shorting strap; mounting the substrate on a portion of a quantum cavity; placing the portion of the quantum cavity in a vacuum chamber; etching away the sacrificial shorting strap in the vacuum chamber while the substrate is mounted to the portion of the quantum cavity, such that the sacrificial shorting strap no longer connects the first electrode paddle and the second electrode paddle; placing the quantum cavity in a cooling chamber for operation, the tunnel junction having been protected from electrostatic discharge by the sacrificial shorting strap; and wherein, when the substrate is mounted on the quantum cavity in the vacuum chamber, an etchant is utilized to etch away the sacrificial shorting strap without removing the tunnel junction, the first electrode paddle, and the second electrode paddle.
A method for protecting a tunnel junction during fabrication. First, form two opposing electrode paddles (first and second) on a substrate. Then, create a sacrificial shorting strap that connects the two electrode paddles. After the strap is in place, form the tunnel junction between the paddles. Mount the substrate onto a quantum cavity, place the cavity in a vacuum chamber, and etch away the shorting strap using an etchant that doesn't harm the tunnel junction or the electrodes, while still inside the vacuum chamber. The shorting strap protects the tunnel junction from electrostatic discharge. Finally, put the quantum cavity in a cooling chamber for operation.
2. The method of claim 1 , wherein the etchant is a wet etchant that does not attack the tunnel junction, the first electrode paddle, and the second electrode paddle.
The tunnel junction protection method, as described above, uses a wet etchant to remove the sacrificial shorting strap. This wet etchant is specifically chosen so that it does not damage or remove the tunnel junction itself, nor does it affect the first and second electrode paddles.
3. The method of claim 1 , wherein the etchant is a dry etchant that does not attack the tunnel junction, the first electrode paddle, and the second electrode paddle.
The tunnel junction protection method, as described above, uses a dry etchant to remove the sacrificial shorting strap. This dry etchant is specifically chosen so that it does not damage or remove the tunnel junction itself, nor does it affect the first and second electrode paddles.
4. The method of claim 3 , wherein the dry etchant is XeF 2 .
The tunnel junction protection method uses a dry etching process, as described above, where the specific dry etchant used to remove the sacrificial shorting strap is Xenon Difluoride (XeF2). This etches the shorting strap away without damaging the tunnel junction or electrodes.
5. The method of claim 1 , wherein, when the substrate is mounted on the quantum cavity in the vacuum chamber, an etchant is utilized to etch away the sacrificial shorting strap, without requiring the sacrificial shorting strap to be cut in order sever the sacrificial shorting strap.
The tunnel junction protection method, as described above, etches away the sacrificial shorting strap while the substrate is mounted on the quantum cavity within a vacuum chamber using a specific etchant. This etching process removes the entire shorting strap without needing to physically cut or sever it into separate pieces. The etchant selectively removes the shorting strap material.
6. The method of claim 1 , wherein, when the substrate is mounted on the quantum cavity in the vacuum chamber, an etchant is utilized to etch away the sacrificial shorting strap, without leaving the sacrificial shorting strap severed into a first part and a second part opposing each other.
The tunnel junction protection method, as described above, etches away the sacrificial shorting strap using a specific etchant while the substrate is mounted to the quantum cavity in the vacuum chamber. This etching process completely removes the strap instead of cutting it into opposing pieces (first and second parts) that would be left still separated on the substrate.
7. The method of claim 1 , wherein the tunnel junction is a Josephson junction.
The tunnel junction used in the protection method, as described above, is a Josephson junction. This type of junction is commonly used in superconducting circuits and benefits from the electrostatic discharge protection provided by the sacrificial shorting strap during fabrication.
8. The method of claim 1 , wherein the tunnel junction comprises a first superconducting electrode and a second superconducting electrode, the first superconducting electrode and the second superconducting electrode sandwiching an insulator layer.
The tunnel junction used in the protection method, as described above, is constructed with a first superconducting electrode and a second superconducting electrode. These electrodes are separated by a thin insulating layer, forming a sandwich structure. The sacrificial shorting strap protects this delicate insulator layer from electrostatic discharge.
9. The method of claim 8 , wherein the sacrificial shorting strap prevents the insulator layer in the tunnel junction from receiving the electrostatic discharge, thus protecting the insulator layer from becoming defective.
In the tunnel junction protection method, as described above, the sacrificial shorting strap prevents electrostatic discharge from reaching and damaging the insulating layer within the tunnel junction. This protection is important because electrostatic discharge can create defects in the insulator, which degrade the performance or completely destroy the tunnel junction.
10. The method of claim 1 , wherein, before etching away the sacrificial shorting strap in the vacuum chamber, one end of the sacrificial shorting strap connects at a first location on the first electrode paddle and another end of the sacrificial shorting strap connects at a second location on the second electrode paddle.
Before the sacrificial shorting strap is etched away within the vacuum chamber (as described in the tunnel junction protection method), the strap is connected between the two electrode paddles. One end of the strap connects at a specific location on the first electrode paddle, and the other end connects at a different specific location on the second electrode paddle.
11. The method of claim 10 , wherein, after etching away the sacrificial shorting strap in the vacuum chamber while the substrate is mounted to the portion of the quantum cavity, the first electrode paddle has a first raised portion at the first location and the second electrode paddle has a second raised portion at the second location.
In the tunnel junction protection method, after the sacrificial shorting strap is etched away while the substrate is mounted on the quantum cavity inside the vacuum chamber, the first electrode paddle retains a small raised portion at the location where the strap connected, and the second electrode paddle similarly retains a small raised portion at its connection location.
12. The method of claim 11 , wherein the first raised portion and the second raised portion are material of the first electrode paddle and the second electrode paddle; wherein the first raised portion of the material has a higher height at the first location than other areas of the material of the first electrode paddle; wherein the second raised portion of the material has a higher height at the second location than other areas of the material of the second electrode paddle.
In the tunnel junction protection method, the raised portions that remain on the first and second electrode paddles (as described above) are formed from the original material of the paddles. These raised portions have a greater height at the connection locations compared to the height of the rest of the paddle material, indicating that the etching process was less aggressive in those specific areas.
13. The method of claim 12 , wherein the one end and the another end of the sacrificial shorting strap covered the first location and the second location during formation of the tunnel junction, thus keeping the material at the first location and the second location from wearing away resulting in the first raised portion and the second raised portion.
In the tunnel junction protection method, during the tunnel junction formation, the ends of the sacrificial shorting strap cover the connection locations on the electrode paddles. This covering keeps the material at these locations from being worn away during the junction formation process, which results in the formation of raised portions at these locations after the shorting strap is removed.
14. The method of claim 10 , wherein the first location includes a residual portion of the sacrificial shorting strap; wherein the second location includes another residual portion of the sacrificial shorting strap; wherein the residual portion and the another residual portion of the sacrificial shorting strap do not overhang from the first and second electrode paddles, respectively.
In the tunnel junction protection method, after the sacrificial shorting strap is removed, a small residual portion of the strap may remain at each connection location on the electrode paddles. Critically, these residual portions do not overhang or extend beyond the edges of the electrode paddles themselves.
15. The method of claim 1 , wherein the quantum cavity is a three-dimensional cavity for operating the tunnel junction within the cooling chamber.
In the tunnel junction protection method, the quantum cavity onto which the substrate is mounted is a three-dimensional (3D) cavity. This 3D cavity provides a specific electromagnetic environment that is optimized for the operation of the tunnel junction after it is placed in the cooling chamber.
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June 24, 2015
July 11, 2017
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